Air assist atomization of the liquid fuel injected from the nozzle of a fuel injector is a known technique that is used to promote better preparation of the combustible air/fuel mixture that is introduced into the combustion chambers of an internal combustion engine. A better mixture preparation promotes both a cleaner and a more efficient combustion process, a desirable goal from the standpoint of both exhaust emissions and fuel economy.
The state of the art contains a substantial number of patents relating to air assist atomization technology. The technology recognizes the benefits that can be gained by the inclusion of special assist air passages that direct the assist air into interaction with the injected liquid fuel. Certain air assist fuel injection systems use pressurized air, from either a pump or some other source of pressurization, as the assist air. Other systems rely on the pressure differential that exists between the atmosphere and the engine's induction system during certain conditions of engine operation. It is a common technique to mount the fuel injectors in an engine manifold or fuel rail which is constructed to include assist air passages for delivering the assist air to the individual injectors.
It is known from commonly assigned U.S. Ser. No. 07/652,166 to construct an air assist atomizer in which the definition of the final length of the assist air passage to each fuel injector tip is provided by the cooperative organization and arrangement of two additional parts which form an atomizer assembly disposed between the nozzle of an injector and the wall of a socket that receives the injector. One advantage of that invention is that it adapts an otherwise conventional electrically-operated fuel injector for use in an air assist system without the need to make modifications to the basic injector, and without the need to make special accommodations in the injector-receiving socket other than suitably dimensioning the socket to accept the air assist atomizer.
The air assist atomizer of the present invention is similar to that of U.S. Ser. No. 07/652,166 in that it comprises the cooperative organization and arrangement of two individual parts; in other respects, as will become apparent from the ensuing description, drawings, and claims, it is distinguished from the air assist atomizer of U.S. Ser. No. 07/652,166.
From Patentschrift DE 40 04 897 C1 it is known to construct a one-piece atomizer with a series of short, circumferentially spaced apart risers on the interior of the atomizer's end wall which abut the end of the nozzle so as to thereby cooperatively define a number of circumferentially spaced apart air assist openings through which assist air passes radially to act upon the injected fuel just after it has left the nozzle. In order to create and to closely control the axial dimension of these air assist openings, it would seem essential to conduct precision machining operations on the interior of the end wall, and since the dimensions involved are small, it may be forecast that such machining operations will be difficult to conduct in a cost-effective manner for mass production of the atomizer.
The present invention is similar to the atomizer disclosed in Patentschrift DE 40 04 897 C1 and other earlier prior art in that it comprises a number of air assist openings that are circumferentially spaced apart and that convey assist air radially inwardly toward the injected fuel; it is distinguished however in that instead of risers, a separate disk is inserted into the interior of a surrounding shroud that is fitted over the nozzle. The disk is disposed axially sandwiched between, and in mutual abutment with, the nozzle and the end wall of the shroud to thereby create the air assist openings through which assist air is radially inwardly directed to the injected fuel that has just left the nozzle. The disk can be advantageously fabricated by conventional stamping technology, and the interior of the shroud can be finished without the ostensibly elaborate measures that may be expected in the case of the atomizer described in the referenced Patentschrift.
Further features, advantages, and benefits of the present invention will be seen in the ensuing description and claims which are accompanied by drawings. These drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.